1. Field of the Disclosure
The present disclosure relates to the field of semiconductor devices and more specifically to an integrated transformer structure and its method of fabrication.
2. Discussion of Related Art
The need for transformers in semiconductor design dictates the use of discrete inductors or spiral inductors. The discrete inductor is in an off-chip, off-package configuration and requires long interconnects to connect the inductor to a chip. These interconnects have high impedances and result in large ohmic losses. Also, discrete inductors require extra space outside the chip package, which is difficult to provide for in high-density circuit board fabrication.
Spiral inductors are created through windings of metal thin films, usually on a semiconductor substrate. The first drawback of spiral inductors includes the large area necessary to create large inductances. Another drawback of spiral inductors includes the tendency of the inductors to have high resistances. This high resistance deteriorates the quality factor of the inductors, making them too lossy for such applications as power delivery. Furthermore, spiral inductors force the magnetic flux into the silicon substrate, causing both eddy current losses and interference with devices.